A very unscientific measure of how profitable a Mac product is how it compares to a similarly priced competitor.
I didn't compare it to a similarly priced competitor???
I simply stated that it's design had remained very similar for 5 years, so it might actually be more profitable on a per unit basis than other Mac models.
This hasn't been true for many years.
You're confusing popularity with status. The iMac is definitely the most popular Mac desktop and very powerful too, but Apple's flagship is their 12 core monster Mac Pro and it will remain so until they release a better Mac Pro or a more Powerful iMac.
That's the iMac or MBP, not the tower. Those are the products that people see in movies and out everywhere in public with the apple logo on it. My local Apple store didn't even have a pro on display the last time I went. Apple isn't even giving it retail space.
Really?
Maybe they'd sold out!

The Apple Store in London had two 27" displays hooked up to the Mac Pro when I last visited earlier this year. It was running Final Cut and had plenty of people swooning over it. iMac's may be what you see in the movies, but the Mac Pro MAKES the movies!
I believe estimates over the past few years do not put Mac Pro orders in the millions of sales per year, which is what apple gets with its other product lines.
What estimates might these be?
Are these the fictitious estimates grabbed out of thin air to suit your argument?
Link please.
And then they keep them for 5-6 years because they were so expensive, and then replace them with iMacs and MBPs, which they order more frequently.
My company upgraded from G5's to Mac Pro's in 2006 and upgraded the Mac Pro's again in 2009 and will upgrade again in 2012 if new Mac Pro's are announced. That's 3 years between purchases - I don't think that's significantly longer than most people keep an iMac.
Of course as they are more expandable, they will remain relevant much longer than an all in one iMac will, but that's hardly a criticism is it?
You can update your graphics card or display whenever you like with a Mac Pro. Adding USB3 or eSATA is a breeze. To do these things on an iMac you have to sell it and buy a new one.
Another demonstration of why the Mac Pro is Apple's flagship computer.
Apple can to just fine without the Pro. Really, they've essentially been doing that for some time already.
Says who?
Mac Pro's are being sold everyday - who are you to say people don't need them?
The amount of responses on this board is a good indication of how important they are to some.
Of course sales might have slowed recently as (like the iPhone 4), people hold off buying in anticipation of the rumoured release of new models, but that's perfectly normal.
Lose the niche, gain the majority.
You gain the majority by keeping the niche.
The niche now is tomorrows mainstream.
You lose the majority when you have no niche, it's the niche that keeps you interesting, cool and aspirational.
That's the case with any Mac. But when someone buys a cheaper, non tower Mac, they have more money to get another Apple product with it. At one of my former jobs, the boss used the budget of replacing one mac pro to get two iMacs instead. That's got to be the story happening all over the place.
Nonsense. Just because 2 iMacs were more suitable for your boss, doesn't make it the case for everyone using a Mac Pro.
If your boss could manage with an iMac, he probably didn't need a Mac Pro to begin with.
Most who really need a Mac Pro, simply could not get by with any other Mac product - it's that simple.